Chinese mitten crab
Encyclopedia
The Chinese mitten crab, Eriocheir sinensis (also known as the big sluice crab and Shanghai hairy crab) is a medium-sized burrow
ing crab
, named for its furry claws that look like mittens, that is native in the coastal estuaries
of eastern Asia
from Korea
in the north to the Fujian
province of China
in the south. It has also been introduced
to Europe
and North America
where it is considered an invasive species
.
width is 30–100 mm (1.2–3.9 ) and the legs are about twice as long as the carapace is wide.
Mitten crabs spend most of their life in fresh water
, but they must return to the sea to breed. During their fourth or fifth year in late summer, the crustaceans migrate
downstream, and attain sexual maturity in the tidal estuaries
. After mating, the females continue seaward, overwintering in deeper waters. They return to brackish water in the spring to hatch their eggs
. After development as larvae
, the juvenile crabs gradually move upstream into fresh water, thus completing the life cycle.
and Europe
, raising concerns that it competes with local species, and its burrowing nature damages embankments and clogs drainage systems. The crabs can make significant inland migrations. It was reported in the London Evening Standard
in 1995 that the residents of Greenwich
saw Chinese mitten crabs coming out of the River Thames
and moving towards the High Street
, and other reports indicate that the crabs have been known to take up residence in swimming pool
s. In some places the crabs have been found hundreds of miles from the sea. There is concern in areas with a substantial native crab fishery, such as the Chesapeake Bay
in Maryland
and the Hudson River
in New York
(both locations where the crabs were first spotted in 2005), as the impact of the invasion by this species on the native population is unknown.
It is generally illegal to import, transport, or possess live Chinese mitten crabs in the United States, as accidental release or escape risks spreading these crabs to uninfested waters. In addition, some states may have their own restrictions on possession of mitten crabs. California allows fishing for mitten crabs with some restrictions.
The Chinese mitten crab has been introduced into the Great Lakes
several times, but have not yet been able to establish a permanent population.
The Smithsonian is tracking the spread of the Chinese mitten crab and seeking help to determine the current distribution status of the mitten crab in the Chesapeake Bay
region. People are encouraged to report any mitten crab sightings, along with details (date, specific location, size) and a close-up photograph or specimen if possible. The first confirmed record along the East coast of the United States
, was in the Chesapeake Bay
near Baltimore
, Maryland in 2005.
The crab is a famous delicacy in Shanghai cuisine
and is prized for the female crab roe. The crab meat is believed by the Chinese to have a "cooling" (yin) effect on the body. Concerns have been raised that the population and origin of the crab may be affected because of overfishing of the species in the Yangtze River
.
Chinese spend hundreds of yuan
just to taste a small crab from Yangcheng Lake
which are considered a delicacy. The crabs cost 680–700 yuan, or roughly US$105, per kilogram. Most of the Yangcheng crabs are exported to Shanghai
and Hong Kong
, and high-profit foreign markets. Responding to the spread of the crab to the West, businessmen have started seeing it as a new source of crab for the Chinese market. One proposed scheme involves importing unwanted crabs from Europe
, where they are seen as a pest, to replenish local pure-bred stock.
Mitten crabs have exhibited a remarkable ability to survive in highly modified aquatic habitats, including polluted waters. Like certain fish, they can also easily tolerate and uptake heavy metals, such as cadmium
and mercury
. Therefore, the farming and post-harvesting of the species needs proper management if it is used as a food.
Recently, China
introduced vending machines to sell this species of crab in the subways. The crabs are stored at 5 °C (41 °F), which induces a sleepy state of hibernation. The prices of the crabs range from around $1.50 to $7.00 (USD). They are guaranteed to be fresh and alive.
Burrow
A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...
ing crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
, named for its furry claws that look like mittens, that is native in the coastal estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
of eastern Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
from Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
in the north to the Fujian
Fujian
' , formerly romanised as Fukien or Huguing or Foukien, is a province on the southeast coast of mainland China. Fujian is bordered by Zhejiang to the north, Jiangxi to the west, and Guangdong to the south. Taiwan lies to the east, across the Taiwan Strait...
province of China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
in the south. It has also been introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
to Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
where it is considered an invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
.
Description and ecology
This species' distinguishing features are the dense patches of dark hair on its claws. The crab's body is the size of a human palm. The carapaceCarapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
width is 30–100 mm (1.2–3.9 ) and the legs are about twice as long as the carapace is wide.
Mitten crabs spend most of their life in fresh water
Fresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
, but they must return to the sea to breed. During their fourth or fifth year in late summer, the crustaceans migrate
Animal migration
Animal migration is the relatively long-distance movement of individuals, usually on a seasonal basis. It is a ubiquitous phenomenon, found in all major animal groups, including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. The trigger for the migration may be local...
downstream, and attain sexual maturity in the tidal estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
. After mating, the females continue seaward, overwintering in deeper waters. They return to brackish water in the spring to hatch their eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
. After development as larvae
Crustacean larvae
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow...
, the juvenile crabs gradually move upstream into fresh water, thus completing the life cycle.
Invasive species
This species has been spread to North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, raising concerns that it competes with local species, and its burrowing nature damages embankments and clogs drainage systems. The crabs can make significant inland migrations. It was reported in the London Evening Standard
Evening Standard
The Evening Standard, now styled the London Evening Standard, is a free local daily newspaper, published Monday–Friday in tabloid format in London. It is the dominant regional evening paper for London and the surrounding area, with coverage of national and international news and City of London...
in 1995 that the residents of Greenwich
Greenwich
Greenwich is a district of south London, England, located in the London Borough of Greenwich.Greenwich is best known for its maritime history and for giving its name to the Greenwich Meridian and Greenwich Mean Time...
saw Chinese mitten crabs coming out of the River Thames
River Thames
The River Thames flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom. While it is best known because its lower reaches flow through central London, the river flows alongside several other towns and cities, including Oxford,...
and moving towards the High Street
High Street
High Street, or the High Street, is a metonym for the generic name of the primary business street of towns or cities, especially in the United Kingdom. It is usually a focal point for shops and retailers in city centres, and is most often used in reference to retailing...
, and other reports indicate that the crabs have been known to take up residence in swimming pool
Swimming pool
A swimming pool, swimming bath, wading pool, or simply a pool, is a container filled with water intended for swimming or water-based recreation. There are many standard sizes; the largest is the Olympic-size swimming pool...
s. In some places the crabs have been found hundreds of miles from the sea. There is concern in areas with a substantial native crab fishery, such as the Chesapeake Bay
Chesapeake Bay
The Chesapeake Bay is the largest estuary in the United States. It lies off the Atlantic Ocean, surrounded by Maryland and Virginia. The Chesapeake Bay's drainage basin covers in the District of Columbia and parts of six states: New York, Pennsylvania, Delaware, Maryland, Virginia, and West...
in Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
and the Hudson River
Hudson River
The Hudson is a river that flows from north to south through eastern New York. The highest official source is at Lake Tear of the Clouds, on the slopes of Mount Marcy in the Adirondack Mountains. The river itself officially begins in Henderson Lake in Newcomb, New York...
in New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
(both locations where the crabs were first spotted in 2005), as the impact of the invasion by this species on the native population is unknown.
It is generally illegal to import, transport, or possess live Chinese mitten crabs in the United States, as accidental release or escape risks spreading these crabs to uninfested waters. In addition, some states may have their own restrictions on possession of mitten crabs. California allows fishing for mitten crabs with some restrictions.
The Chinese mitten crab has been introduced into the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
several times, but have not yet been able to establish a permanent population.
The Smithsonian is tracking the spread of the Chinese mitten crab and seeking help to determine the current distribution status of the mitten crab in the Chesapeake Bay
Chesapeake Bay
The Chesapeake Bay is the largest estuary in the United States. It lies off the Atlantic Ocean, surrounded by Maryland and Virginia. The Chesapeake Bay's drainage basin covers in the District of Columbia and parts of six states: New York, Pennsylvania, Delaware, Maryland, Virginia, and West...
region. People are encouraged to report any mitten crab sightings, along with details (date, specific location, size) and a close-up photograph or specimen if possible. The first confirmed record along the East coast of the United States
East Coast of the United States
The East Coast of the United States, also known as the Eastern Seaboard, refers to the easternmost coastal states in the United States, which touch the Atlantic Ocean and stretch up to Canada. The term includes the U.S...
, was in the Chesapeake Bay
Chesapeake Bay
The Chesapeake Bay is the largest estuary in the United States. It lies off the Atlantic Ocean, surrounded by Maryland and Virginia. The Chesapeake Bay's drainage basin covers in the District of Columbia and parts of six states: New York, Pennsylvania, Delaware, Maryland, Virginia, and West...
near Baltimore
Baltimore
Baltimore is the largest independent city in the United States and the largest city and cultural center of the US state of Maryland. The city is located in central Maryland along the tidal portion of the Patapsco River, an arm of the Chesapeake Bay. Baltimore is sometimes referred to as Baltimore...
, Maryland in 2005.
Culinary
Shanghai cuisine
Shanghai cuisine , also known as Hu cai is a popular style of Chinese cuisine. The city of Shanghai itself does not have a separate and unique cuisine of its own, but modifies those of the surrounding provinces, is Jiangsu and Zhejiang coastal provinces. What can be called Shanghai cuisine is...
and is prized for the female crab roe. The crab meat is believed by the Chinese to have a "cooling" (yin) effect on the body. Concerns have been raised that the population and origin of the crab may be affected because of overfishing of the species in the Yangtze River
Yangtze River
The Yangtze, Yangzi or Cháng Jiāng is the longest river in Asia, and the third-longest in the world. It flows for from the glaciers on the Tibetan Plateau in Qinghai eastward across southwest, central and eastern China before emptying into the East China Sea at Shanghai. It is also one of the...
.
Chinese spend hundreds of yuan
Renminbi
The Renminbi is the official currency of the People's Republic of China . Renminbi is legal tender in mainland China, but not in Hong Kong or Macau. It is issued by the People's Bank of China, the monetary authority of the PRC...
just to taste a small crab from Yangcheng Lake
Yangcheng Lake
Yangcheng Lake is a freshwater lake about northeast of the city of Suzhou in Jiangsu Province, China. It is the most famous area of origin for the Chinese mitten crabs which are a considered a delicacy....
which are considered a delicacy. The crabs cost 680–700 yuan, or roughly US$105, per kilogram. Most of the Yangcheng crabs are exported to Shanghai
Shanghai
Shanghai is the largest city by population in China and the largest city proper in the world. It is one of the four province-level municipalities in the People's Republic of China, with a total population of over 23 million as of 2010...
and Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
, and high-profit foreign markets. Responding to the spread of the crab to the West, businessmen have started seeing it as a new source of crab for the Chinese market. One proposed scheme involves importing unwanted crabs from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, where they are seen as a pest, to replenish local pure-bred stock.
Mitten crabs have exhibited a remarkable ability to survive in highly modified aquatic habitats, including polluted waters. Like certain fish, they can also easily tolerate and uptake heavy metals, such as cadmium
Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
and mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
. Therefore, the farming and post-harvesting of the species needs proper management if it is used as a food.
Recently, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
introduced vending machines to sell this species of crab in the subways. The crabs are stored at 5 °C (41 °F), which induces a sleepy state of hibernation. The prices of the crabs range from around $1.50 to $7.00 (USD). They are guaranteed to be fresh and alive.
External links
- Species Profile – Chinese mitten crab (Eriocheir sinensis), National Invasive Species Information Center, United States National Agricultural LibraryUnited States National Agricultural LibraryThe United States National Agricultural Library is one of the world's largest agricultural research libraries, and serves as a National Library of the United States and as the library of the United States Department of Agriculture...
- Mitten Crab Watch - Smithsonian Environmental Research Center